Key Engineering Materials Vol. 694

Abstract: The tensile properties and morphological studies of linear low density polyethylene (LLDPE)/poly (vinyl alcohol) (PVA)/kenaf (KNF) composites with and without 3-(trimethoxysilyl) propyl methacrylate (silane coupling agent) were investigated. The composites with different KNF loading (10, 20, 30, 40 phr) were prepared using a Thermo Haake Polydrive internal mixer at 150°C and 50 rpm for 10 min. The results indicated that composites with 3-(trimethoxysilyl) propyl methacrylate gives higher tensile strength and modulus but lower elongation at break than composites without. The presence of 3-(trimethoxysilyl) propyl methacrylate found to enhance the interfacial adhesion between LLDPE/PVA matrix and KNF fiber. Morphological studies on tensile fractured surfaces showed good adhesion between LLDPE/PVA matrix and KNF, and better dispersion of KNF for the composites with 3-(trimethoxysilyl) propyl methacrylate.

Abstract: The aim of this study is to evaluate the mechanical properties and study the failure of laminated glass reinforced composite coated with gelcoat of different thickness. Firstly, the gelcoat was applied to the mould using brush and subsequently, glass fiber reinforced composite laminates were fabricated on it using vacuum bagging technique. The mechanical properties of the composites various were tested by using tensile and three-point flexural tests. The fracture behaviour of different gelcoat thickness was observed using scanning electron microscope (SEM) to determine the failure behaviour that occurred. The flexural test was performed in two ways, i.e., gelcoat layer facing top and facing down. For both flexural tests, composite coated with 0.30 mm thick of gelcoat shows the highest mechanical strength. Tensile test is useful to investigate the interfacial bonding in between gelcoat and laminate composite. The composite coated with 0.40 mm of gelcoat showed the highest tensile strength, an increase of 38 % compared to the uncoated composite. It was observed that an increase in gelcoat thickness increased the brittleness of the laminated composite. From the failure analysis, failures were caused by the delamination of matrix between the plies, while the gelcoat was still strongly bonded with composite laminate.

Abstract: An experimental study was conducted to investigate the influence of thermo-oxidative ageing on the tensile properties of PVC/ENR/KCP composites. Sodium dodecyl sulfate filler treatment was also carried out to evaluate the effect of filler treatment. The composites were prepared by melt compounding using Haake Polydrive internal mixer at 140 °C and 50 rpm. Compression-moulded samples were subjected to fracture surface morphology analysis and thermo-oxidative ageing for 3, 5 and 7 days. Thermo-oxidative ageing test indicates that after 3 days of exposure to heat, tensile strength increases, which is due to the further cross-linking reaction. With further exposure for 5 days and 7 days, the tensile strength is reduced probably due to the reduction in flexibility of the cross-link, which affect the stress distribution in the composites.

Abstract: This research work investigates the effect of using alkaline-treated continuous long pineapple leaf fibers (PALF) as reinforcement in bio-based poly lactic acid (PLA) polymer biocomposite. Alkaline treatment using NaOH solution was employed to improve the fiber-matrix adhesion, with the aim to enhance the mechanical properties of the biocomposites, in terms of its tensile and impact properties. In this study, both the plain PLA polymer and the PALF reinforced PLA biocomposites were prepared using compression moulding process. Thin films with nominal thickness of approximately 1 mm each were stacked in between continuous long PALF fibers prior to compression moulding via hot press machine to form biocomposites plate. Two types of mechanical testing were performed, i.e., tensile test (ASTM D3039) and impact test (ASTM D6110). Significant enhancements are observed when the plain PLA were reinforced with the PALF long fiber, with the biocomposites showing two times better the tensile strength and modulus, with the values of approximately 73.26 MPa in comparison to only about 34.85 MPa for the plain PLA and tensile modulus of approximately 2735.36 MPa in comparison to 1641.12 MPa for the plain PLA. The energy absorption of the biocomposites also showed promising results with a value of approximately 0.92 J/cm² in comparison to only about 0.35 J/cm² for the plain PLA. In addition, a scanning electron microscope (SEM) was used to scrutinize morphology of the PALF reinforced PLA biocomposites.

Abstract: The application of natural fibers in composite is very encouraging because of its many benefits such as more environmental friendly and cost reduction. Recently, there is an interest on the application of kenaf-based material for high-end uses such as in automotive industry. In this research, mechanical properties of kenaf fiber reinforced polypropylene (KFRP) composite added with two different types of bio-based fillers, i.e., oil palm shell particle (OPSP) and rubber seed shell particle (RSSP) are studied. The composites were prepared by melt mixing of the materials using internal mixer, followed by compression molding process using hot press machine. The tensile and flexural strength were found to increase with the addition of OPSP as well as RSSP. However, KFRP composite added with RSSP showed better tensile, flexural and impact properties as compared to the composite added with OPSP. From microscopic observation of the raw OPSP and RSSP particles, it was observed that OPSP showed a more granular shape, while RSSP particles were flakier in shape. This difference in particle shape is believed to affect the mechanical properties of the composites as demonstrated in this study.

Abstract: Kenaf fibers were immersed in 6% solution of sodium hydroxide (NaOH) for 1, 2, 3, 4 and 5 hours. The treated fibers were characterized with X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The XPS results showed that the alkali treatment increased the proportion of oxygen atoms on the fiber surface as indicated by the increase in oxygen-carbon ratio. An increase in C2 peak (C-OH bonds) was also observed suggesting the present of cellulose on the fiber surface. The decrease in C1 peak (C-C bonds) suggested that lignin was removed from the fiber surface following the alkali treatment. Scale-like structures were observed from the AFM topographic images to indicate the presence of cellulose microfibrils in the primary cell wall of the treated fiber. Alkali treated fiber surface showed lower mean surface roughness than the untreated fiber indicating smoother fiber surface. The fiber surface became relatively smooth after the alkali treatment due to the removal of non-cellulosic layer.

Abstract: Glass-composite materials were prepared from the soda lime silicate (SLS) waste glass; ball clay and charcoal powder were fired to temperature of 850 °C as an effort for recycling waste glass. Various carbon contents, i.e., 1, 5, 10, 20 and 30 wt.% C were used to evaluate the effect of carbon contents on the hardness and thermal properties of glass composites. In addition, five different particles size (d_0.5) of 1, 5, 20, 40 and 75 μm were used to observe the influence of particle size on the physical and mechanical properties of the glass composites. Phase analysis studies revealed the presence of quartz (ICDD: 00001-0649, 2θ = 25.6° and 35.6°), cristobalite (ICDD 00004-0379, 2θ = 22.0° and 38.4°) and wollastonite (ICDD 00002-0689, 2θ = 30.1° and 26.9°). The results showed that the optimised properties is at 1 wt.% of carbon content containing average pore size of 10 μm, with lowest porosity percentage of 1.76 %, highest Vickers microhardness of 4.6 GPa and minimum CTE. The percentage of porosity and hardness value also increased with reduction in carbon particle size.

Abstract: Most of the electromagnetic (EM) wave absorbers are commonly made from polymer-based materials. A large number of polymers are resistant to the environmental degradation and are thus responsible for the buildup of polymeric solid waste materials. These solid wastes cause acute environmental problems and remain undegraded for quite a long time. In a view of the awareness and concern for the problems created by the polymeric solid wastes, new biodegradable cellulosic composite with low cost and nontoxic materials, have been designed and developed. However, the properties of natural fibers that tends to absorb water, thus limiting their application. In this study, precipitated calcium carbonate (PCC) was added with stearic acid (SA) in order to generate a hydrophobic coating formulation. PCC works as filler and SA acts as surface hydrophobic modification agent. Polymer latex was then added to the coating compound as the binder. The composite surface morphology was inspected using scanning electron microscope (SEM). Results show that durian peel composite sheet had successfully achieved a superhydrophobic surface with a water contact angle of 154.85° which exceed 150°.

Abstract: Copper-based metal-organic framework (MOF-199, also known as Cu-BTC and HKUST-1) materials were successfully synthesized by hydrothermal method using renewable straight-chain fatty alcohol with eight carbon chain length (i.e. octyl alcohol). The addition of palm oil derived fatty alcohol (PODFA) was suggested to act as porogen (structure directing agent) that aided the particle formation and flexible porous structure. This synthesis approach was environmental-friendly and sustainable by utilizing the fatty alcohols originated from biomass such as palm oil. The resulting MOF-199 materials exhibited single crystalline octahedral morphology structure by X-ray diffraction analyses and SEM images. The optimum ratio of octyl alcohol exhibited well-defined single octahedral particles at size range of ca. 10-50 µm and reduced by-product formation of cuprous oxide at high temperature synthesis. The nature of MOF-199 having apparently high surface area, high pore volume and low density provided the possibility in carbon capture storage. The CO₂ adsorption capacity of MOF-199 investigated using high pressure volumetric analyser (HPVA-II) at ambient temperature (i.e. 25 °C) was found to be at maximum working capacity.